JP2010199621A - Multilayer ceramic substrate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make a bonding material which is set to be less likely to climb up along the inner face of the cavity, and to make a nozzle for introducing the adhesive material easy to inserted into the cavity in a multi layer ceramic substrate provided with a cavity for accommodating an electrical component in a bonded state via a bonding material as underfill resin. <P>SOLUTION: A longitudinal projection 13, extending in parallel to the inner bottom plane 8 of the cavity 4, is formed in the inside face 12a of the cavity 4 so as not to prevent the adhesive material 9 from climbing over the project 13. A projection 13 is not formed on at least one inside plane 12b in the cavity 4, for leave a space that allows the nozzle 18 for introducing the adhesive material to be inserted in the cavity 4. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a multilayer ceramic substrate, and more particularly, to a multilayer ceramic substrate including a cavity for accommodating electronic components in a state of being bonded via a bonding material.

  For example, a multilayer ceramic substrate is used to realize a package structure of an electronic component such as a semiconductor element. In this case, a cavity is provided in the multilayer ceramic substrate, and electronic components such as semiconductor elements are accommodated in the cavity.

  According to the package structure as described above, electronic components can be accommodated in the cavity, and necessary wiring and passive elements can be formed on the multilayer ceramic substrate. Can respond to functionalization.

  Under such circumstances, as the multilayer ceramic substrate is further miniaturized, the cavity needs to be made smaller. On the other hand, the electronic component housed in the cavity is usually bonded to the inner bottom surface of the cavity via a bonding material. In this case, as described above, when the cavity is made small, it is necessary to reduce the amount of the bonding material used accordingly. Depending on the situation in which the bonding material is used, the bonding material is simply an electrically insulating adhesive for mechanical bonding, or a conductive material such as solder or conductive adhesive that also achieves electrical connection. May be sex.

  However, the bonding material is usually injected into the cavity using a syringe, but there is a problem that it is difficult to stably adjust the injection amount within a very small range. Therefore, in order to solve this problem as much as possible, in general, a large amount of bonding material is set. This is because if the amount of the bonding material is small, a fatal problem that the electronic component is not fixed in the cavity occurs.

  As described above, when the amount of the bonding material is increased, the bonding material is applied to the inner bottom surface in the cavity, and then, when the electronic component is placed in the cavity, the bonding material scoops along the inner surface of the cavity. It is hard to avoid going up. When the bonding material crawls up along the inner surface of the cavity, it undesirably adheres to the upper surface of the electronic component, adheres to the surrounding area of the cavity in the multilayer ceramic substrate, or a step is formed in the cavity. In some cases, it may adhere to an upwardly facing surface in the cavity, such as the upper surface of the stepped portion. Then, the adhesion of the bonding material as described above to an undesired portion, for example, hinders wire bonding performed between the electronic component and the multilayer ceramic substrate, or when the bonding material is conductive. May cause undesired electrical shorts.

  As a technique that can solve the above-described problem, for example, there is one described in Japanese Patent Laid-Open No. 2003-124381 (Patent Document 1).

  In Patent Document 1, a multilayer ceramic substrate 51 as shown in FIG. 11 is described. The multilayer ceramic substrate 51 includes a plurality of laminated ceramic layers 52. The multilayer ceramic substrate 51 has a cavity 54 having an opening 53 on one end side in the stacking direction of the ceramic layers 52.

  A semiconductor element 55 is accommodated in the cavity 54. The semiconductor element 55 is fixed in the cavity 54 by a bonding material 57 applied on the inner bottom surface 56 of the cavity 54.

  The semiconductor element 55 is electrically connected to the conductor film 58 on the multilayer ceramic substrate 51 side by wire bonding. FIG. 11 shows a wire 59 formed by wire bonding.

  In the multilayer ceramic substrate 51 having such a configuration, among the plurality of ceramic layers 52 provided with the through holes 60 or 61 to be the cavities 54, the dimension of the through hole 60 is the lowest for the bottom ceramic layer 52. It is characterized in that it is larger than the dimension of the through-hole 61 provided in the cavity, and thereby a recess 62 is formed on the inner surface of the cavity 54.

  According to the structure described in Patent Document 1, the bonding material 57 that is going to crawl up along the inner surface of the cavity 54 can be retained in the recess 62. Therefore, it is possible to suppress the bonding material 57 from creeping up to the upper surface of the semiconductor element 55 and the peripheral region of the cavity 54, that is, the conductor film 58.

  However, the structure described in Patent Document 1 may cause the following problems as problems in the manufacturing process for obtaining the structure.

  That is, when it is going to manufacture the multilayer ceramic substrate 51, as shown in FIG. 12, the several ceramic green sheet 65 which should become the ceramic layer 52 is prepared, and as above-mentioned in the specific ceramic green sheet 65, A through hole 60 or 61 to be the cavity 54 is provided. At this time, for the lowermost ceramic green sheet 65, the dimension of the through hole 60 is made larger than the dimension of the through hole 61 provided in the other ceramic green sheet 65. Next, a plurality of ceramic green sheets 65 including the ceramic green sheet 65 provided with the through holes 60 or 61 are laminated and pressed.

  However, as a result of the pressing process described above, in the ceramic green sheet 65 positioned immediately above the ceramic green sheet 65 provided with the relatively large through-hole 60, as shown by the broken line in FIG. May be deformed so that the surrounding portion that defines the angle hangs downward. As a result, the concave portion 62 to be formed on the inner surface of the cavity 54 may be crushed, and the joint material 57 may not be able to function sufficiently to suppress the creeping-up.

  As the simplest solution for suppressing the creeping of the bonding material along the inner surface of the cavity, it is conceivable to increase the distance between the inner surface of the cavity and the electronic component accommodated therein. For example, if this interval is 200 μm or more, it is said that scooping can be sufficiently suppressed. However, if the interval is increased to 200 μm or more, the dimension of the cavity must be designed to be 400 μm or more larger than the planar dimension of the electronic component. For this reason, an increase in the size of the multilayer ceramic substrate is incurred, which goes against the demand for downsizing of electronic devices.

JP 2003-124381 A

  Therefore, an object of the present invention is to provide a multilayer ceramic substrate structure that can solve the above-described problems.

  The present invention includes a cavity having a plurality of laminated ceramic layers and having an opening formed on one end side in the lamination direction of the ceramic layers, and an electronic component housed in the cavity, and an inner bottom surface of the cavity and the electronic component And a multi-layer ceramic substrate further comprising a bonding material for bonding the two. The cavity provides a rectangular parallelepiped space defined by four inner surfaces.

  In such a multilayer ceramic substrate, according to the present invention, a longitudinal protrusion extending in a direction parallel to the inner bottom surface of the cavity is formed on the inner surface of the cavity, and the protrusion is at least one of the four inner surfaces. It is characterized by not being formed on the inner surface.

  In the multilayer ceramic substrate according to the present invention, it is preferable that the plurality of projecting portions are formed so as to be distributed at a plurality of locations having different height positions on the inner side surface of the cavity.

  In the multilayer ceramic substrate according to the present invention, the protruding portion preferably has an overhang length measured in a direction parallel to the inner bottom surface of the cavity of 0.01 to 0.2 mm. Are provided at different height positions, the lower limit of the overhang length may be shortened to 0.005 mm.

  In the multilayer ceramic substrate according to the present invention, preferably, the bonding material is suppressed from creeping along the inner side surface of the cavity by the protruding portion. As described above, when the plurality of protrusions are formed at different heights, the bonding material does not crawl along the inner surface of the cavity beyond at least the protrusion closest to the opening. It only has to be done.

  According to the multilayer ceramic substrate according to the present invention, since the long protrusion extending in the direction parallel to the inner bottom surface of the cavity is formed on the inner side surface of the cavity, the electronic component housed in the cavity is placed on the inner bottom surface of the cavity. It is possible to advantageously suppress the bonding material for bonding to the surface from rising along the inner surface of the cavity. As a result, the cavity can be downsized, and the multilayer ceramic substrate can be downsized accordingly. In addition, since it is possible to prevent the bonding material from adhering to the upper surface of the electronic component in the cavity, the peripheral area of the cavity, or the surface facing upward in the cavity, for example, reliability of electrical connection by wire bonding or electrical insulation The reliability of the property can be improved, and the production yield of the multilayer ceramic substrate can be improved.

  In addition, when the electronic component accommodated in a cavity is mounted via a bump electrode, underfill resin as a bonding material is filled between the electronic component and the inner bottom surface of the cavity. In this case, since the distance between the electronic component and the inner bottom surface of the cavity is very narrow, the absolute amount of the underfill resin is also very small. For this reason, if even a small amount of the underfill resin crawls up along the inner surface of the cavity, the amount of the underfill resin to be filled between the electronic component and the inner bottom surface of the cavity is insufficient, and voids are generated. , Significantly reduce the reliability. On the other hand, as the underfill resin, one having good wettability is generally used in order to smoothly enter a narrow space between the electronic component and the inner bottom surface of the cavity. Therefore, it can be said that the underfill resin has a property that it tends to creep up along the inner surface of the cavity. Considering these backgrounds, it can be seen that when the underfill resin is used as a bonding material, the existence significance of the protruding portion that can effectively suppress the creeping-up is very large.

  In the multilayer ceramic substrate according to the present invention, when the plurality of projecting portions are formed so as to be distributed at a plurality of locations having different height positions on the inner side surface of the cavity, the above-described creeping-up effect of the bonding material is suppressed. Can be further enhanced. This is because it is sufficient that the bonding material is prevented from creeping along the inner surface of the cavity at least beyond the protrusion closest to the opening.

  Further, when the protruding length of the protruding portion is set to 0.01 to 0.2 mm, it is possible to more reliably suppress the rise of the bonding material while preventing the cavity from being enlarged. In this regard, as described above, when a plurality of protrusions are provided, even if the overhang length is reduced to 0.005 mm, the creeping of the bonding material can be reliably suppressed.

  The multilayer ceramic substrate according to the present invention can be manufactured, for example, by the following manufacturing method.

  First, a plurality of laminated ceramic green layers for a substrate containing ceramic material powder for a substrate are provided, and a cavity for forming an opening is formed on one end side in the laminating direction of the ceramic green layers for a substrate. Between the green layers, an interlayer constraining layer including an inorganic material powder for shrinkage suppression that does not substantially sinter at the sintering temperature of the substrate ceramic material powder is formed so as to be located in at least a part of the peripheral region of the cavity. A raw laminate is produced.

  Next, the raw laminate is fired at a temperature at which the ceramic material powder for substrate sinters but the inorganic material powder for suppressing shrinkage does not substantially sinter. Therefore, in this firing step, the ceramic green layer for a substrate contracts more greatly than the interlayer constraining layer, whereby a long protrusion by the interlayer constraining layer is formed on the inner side surface of the cavity.

  According to the manufacturing method described above, the long protrusion is formed on the inner side surface of the cavity by utilizing the difference in contraction between the interlayer constraining layer and the ceramic green layer for the substrate in the firing step. Therefore, in the stage before firing, the protrusions are not yet formed. For example, in the process of pressing the raw laminate, the problem that the protrusions deform undesirably can be encountered. Absent. Therefore, the protrusion part which has a desired form can be formed stably.

  According to the multilayer ceramic substrate according to the present invention, the cavity provides a rectangular parallelepiped space defined by the four inner surfaces, but the protrusions are not formed on all the four inner surfaces. It is not formed on at least one inner surface of the two inner surfaces. As described above, when the protrusions are not formed on all the four inner surfaces, in the above-described manufacturing method for obtaining this structure, the interlayer constraining layer is positioned only in a part of the peripheral region of the cavity. Since it should just be formed, it can make it difficult to produce the problem of curvature.

  Further, as described above, since the protruding portion is not formed on at least one inner side surface, the protruding portion only needs to be formed in a portion where the rise of the bonding material becomes a problem. As a part where the above-described climbing of the bonding material becomes a problem, there are the following parts.

  That is, when the electronic component accommodated in the cavity is mounted by performing wire bonding, the wire bonding is performed on, for example, only three sides among the four sides of the upper surface of the electronic component. In some cases, the wire bonding is not performed on at least one side. In such a case, as for the side where wire bonding is performed, the climbing of the bonding material hinders proper wire bonding, but for the side where wire bonding is not performed, the climbing of the bonding material is a problem. It will not be. Therefore, it is only necessary to form the protruding portion only on the inner side surface of the cavity close to the side to which wire bonding is applied, in which the rise of the bonding material becomes a problem.

  Further, when the electronic component accommodated in the cavity is to be flip-chip mounted, a nozzle is inserted between the electronic component in the cavity and the inner surface of the cavity in order to fill the underfill resin. . At this time, in order to provide a space allowing insertion of the nozzle while minimizing the area of the inner bottom surface of the cavity so as not to increase the size of the cavity, the electronic component is opposite to the side where the nozzle is inserted. It is preferable to arrange in a state closer to the inner surface side of the. As a result, the joining material tends to creep up on the inner side closer to the electronic component. Therefore, the creeping-up of the bonding material can be effectively suppressed only by forming the protruding portion only on the inner surface closer to such an electronic component.

1 is a cross-sectional view schematically showing a multilayer ceramic substrate 1 as a first reference example. It is sectional drawing which expands and shows the principal part of the multilayer ceramic substrate 1 shown in FIG. It is a figure which expands and shows partially the cross section in alignment with line AA of FIG. It is sectional drawing which shows the raw laminated body 21 produced in order to manufacture the multilayer ceramic substrate 1 shown in FIG. 1 schematically. It is sectional drawing corresponding to FIG. 1 which shows the multilayer ceramic substrate 1a as a 2nd reference example typically. FIG. 6 is a view corresponding to FIG. 2 showing an enlarged main part of the multilayer ceramic substrate 1 a shown in FIG. 5. It is a figure corresponding to FIG. 1 which shows the multilayer ceramic substrate 1b by 1st Embodiment of this invention. It is sectional drawing corresponding to FIG. 3 about the multilayer ceramic substrate 1b shown in FIG. FIG. 8 is a view corresponding to FIG. 1 or 7 schematically showing a multilayer ceramic substrate 1 c according to a second embodiment of the present invention. FIG. 10 is a view corresponding to FIG. 1, schematically showing a multilayer ceramic substrate 1 d as a third reference example of the present invention. It is sectional drawing which shows schematically the multilayer ceramic substrate 51 as a prior art interested in this invention. It is sectional drawing which expands and shows the principal part of the raw laminated body produced in order to manufacture the multilayer ceramic substrate 51 shown in FIG.

  FIGS. 1 to 4 are for explaining a first reference example which is not within the scope of the present invention but is necessary for understanding the present invention. FIG. 1 is a sectional view schematically showing a multilayer ceramic substrate 1. FIG. 2 is an enlarged cross-sectional view showing the main part of the multilayer ceramic substrate 1 shown in FIG. FIG. 3 is a partially enlarged view showing a cross section taken along line AA in FIG.

  The multilayer ceramic substrate 1 includes a plurality of laminated ceramic layers 2. The multilayer ceramic substrate 1 has a cavity 4 having an opening 3 on one end side in the stacking direction of the ceramic layers 2.

  The multilayer ceramic substrate 1 includes various wiring conductors. As the wiring conductor, there are several conductor films 5 formed along the main surface of the specific ceramic layer 2 and several via-hole conductors 6 extending so as to penetrate the specific ceramic layer 2. The conductor film 5 includes those formed on the outer surface of the multilayer ceramic substrate 1 and those formed inside.

  An electronic component 7 such as a semiconductor element is accommodated in the cavity 4. The electronic component 7 is fixed in the cavity 4 by a bonding material 9 provided on the inner bottom surface 8 of the cavity 4. Depending on the mounting structure of the electronic component 7, the bonding material 9 may be made of an insulating resin or may be made of a conductive material such as solder or conductive paste. When the electronic component 7 is mounted on the inner bottom surface 8 of the cavity 4 via the bump electrode (not shown), an underfill resin is filled between the electronic component 7 and the inner bottom surface 8. However, the bonding material 9 may constitute such an underfill resin.

  The electronic component 7 is electrically connected to the conductor film 5 on the multilayer ceramic substrate 1 side by wire bonding. FIG. 1 shows a wire 10 formed by wire bonding. A step portion 11 is formed in the cavity 4, and the conductor film 5 to which the wire 10 is connected is located on the step portion 11.

  In the multilayer ceramic substrate 1 having such a configuration, as a characteristic feature of this reference example, a long protrusion 13 extending in a direction parallel to the inner bottom surface 8 of the cavity 4 is formed on the inner surface 12 of the cavity 4. ing. Further, in this reference example, the plurality of protrusions 13 are formed so as to be distributed at a plurality of locations on the inner surface 12 of the cavity 4 at different height positions. These characteristic configurations, that is, a configuration in which a long protrusion 13 extending in a direction parallel to the inner bottom surface 8 of the cavity 4 is formed on the inner surface 12 of the cavity 4, and a plurality of the protrusions 13 are formed in the cavity 4. The configuration of being distributed so as to be distributed at a plurality of locations having different height positions on the inner side surface 12 can also be applied to the present invention.

  These protrusions 13 act so as to prevent the bonding material 9 from scooping up along the inner surface 12 of the cavity 4 in an uncured stage. In FIG. 1, a state in which the bonding material 9 is prevented from scooping over the protruding portion 13 closest to the inner bottom surface 8 of the cavity 4 is illustrated, but as illustrated, a plurality of protruding portions 13 are formed. In the case where it is formed, it is sufficient that the bonding material 9 is prevented from scooping up beyond the protruding portion 13 closest to the opening 3.

  As shown in FIG. 2, the protruding portion 13 is preferably selected so that the overhang length L measured in a direction parallel to the inner bottom surface 8 of the cavity 4 is 0.01 to 0.2 mm. In this way, by selecting the overhang length L in the range of 0.01 to 0.2 mm, it is possible to reliably suppress the creeping of the bonding material 9 without increasing the size of the cavity 4. When a plurality of protrusions 13 are formed as in this reference example, even if the lower limit value of the overhang length L described above is shortened to 0.005 mm, the bonding material 9 becomes the electronic component 7. As a result, it is possible to reliably suppress the creeping up to the upper surface of the substrate 4 or the peripheral region of the cavity 4, more specifically, the upper surface of the step portion 11.

  1 to 3, the interlayer constraining layer 14 is shown. This interlayer constrained layer 14 plays an important role in forming the protruding portion 13.

  Next, a method for manufacturing the multilayer ceramic substrate 1 will be described. The function of the interlayer constraining layer 14 will be apparent from the description of the method for manufacturing the multilayer ceramic substrate 1.

  FIG. 4 is a cross-sectional view schematically showing a raw laminate 21 produced for manufacturing the multilayer ceramic substrate 1. The raw laminate 21 includes elements corresponding to the elements included in the multilayer ceramic substrate 1 shown in FIG. Therefore, in FIG. 4, elements corresponding to those shown in FIG. 1 are denoted by the same reference symbols unless otherwise hindered, and redundant description may be omitted.

  The raw laminated body 21 includes a plurality of laminated ceramic green layers 22 for a substrate to be the ceramic layer 2. The substrate ceramic green layer 22 includes a substrate ceramic material powder. As the substrate ceramic material, for example, a low-temperature sintered ceramic material that can be sintered at a relatively low temperature such as 1000 ° C. or lower is advantageously used.

  As a low-temperature sintered ceramic material, for example, a material having a composition that generates glass in a firing process, such as a mixture of barium oxide, silicon oxide, alumina, calcium oxide, and boron oxide can be used. Alternatively, a mixture of a ceramic that becomes a filler such as alumina and a glass that acts as a sintering aid such as borosilicate glass or silicon oxide can be used.

  The raw laminate 21 has a cavity 4 that has been formed in the multilayer ceramic substrate 1. The cavity 4 has an opening 3 formed on one end side in the stacking direction of the ceramic green layer 22 for a substrate.

  The raw laminated body 21 is also formed with the conductor film 5 and the via-hole conductor 6 provided in the multilayer ceramic substrate 1.

  Furthermore, an interlayer constraining layer 14 is formed on the raw laminate 21. The interlayer constrained layer 14 includes an inorganic material powder for suppressing shrinkage that is not substantially sintered at the sintering temperature of the ceramic material powder for a substrate described above. As the shrinkage-inhibiting inorganic material powder, for example, oxide inorganic material powder such as alumina, zirconia, magnesia, mullite, quartz, or non-oxide inorganic material powder such as boron nitride can be used. The interlayer constraining layer 14 is formed so as to be located only in the peripheral region of the cavity 4 as well shown in FIG.

  In order to produce such a raw laminate 21, the following steps are preferably performed.

  First, a plurality of substrate ceramic green sheets having a thickness of, for example, about 20 to 200 μm to be the substrate ceramic green layer 22 are prepared.

  Next, through-holes for the via-hole conductors 6 are respectively provided in specific ones of the ceramic green sheets for substrates, and the via-hole conductors 6 are formed by filling the conductive holes in the through-holes.

  In addition, a conductive paste is printed with a predetermined pattern on a specific ceramic green sheet for a substrate, whereby the conductor film 5 is formed.

  Further, an interlayer constraining layer 14 having a thickness of about 1 to 10 μm, for example, is formed on a specific substrate ceramic green sheet. In order to form the interlayer constrained layer 14, it is preferable to perform a step of applying the inorganic material paste containing the above-described shrinkage-suppressing inorganic material powder onto the ceramic green sheet for a substrate by printing or the like. By adopting such a process, the interlayer constraining layer 14 can be easily formed in an arbitrary place with an arbitrary pattern. In addition, since the interlayer constraining layer 14 can be formed by applying the same type of process as the process for forming the conductor film 5, the process for forming the interlayer constraining layer 14 can be simplified. The interlayer constraining layer 14 can be formed efficiently. Instead of adopting the above-described steps, a green sheet containing the inorganic material powder for shrinkage suppression may be formed in advance and laminated on the ceramic green sheet for substrates.

  The order in which the steps of forming the via-hole conductor 6, the step of forming the conductor film 5, and the step of forming the interlayer constraining layer 14 can be arbitrarily changed.

  Next, the process of providing the through-hole which should become the cavity 4 in the several ceramic green sheet for board | substrates containing the ceramic green sheet for board | substrates in which the interlayer constrained layer 14 was formed is implemented. If a through hole to be the cavity 4 is provided after the interlayer constraining layer 14 is formed, the paste material constituting the interlayer constraining layer 14 can be prevented from dripping onto the inner peripheral surface of the through hole. it can. If such an advantage is not desired, the interlayer constraining layer 14 may be formed after the through hole is provided.

  Next, as described above, a plurality of substrate ceramic green sheets including a substrate ceramic green sheet provided with a through hole are stacked and pressed by, for example, an isostatic pressure method. At this stage, since the protruding portion 13 is not formed on the inner side surface 12 of the cavity 4, a problem that the protruding portion 13 is undesirably deformed in the pressing process cannot be encountered.

  In this reference example, as shown in FIG. 4, an outer restraint containing a shrinkage-suppressing inorganic material powder that does not substantially sinter at the sintering temperature of the substrate ceramic material powder on the main surface of the raw laminate 21. Layers 23 and 24 are formed. The shrinkage-inhibiting inorganic material powder contained in the outer constraining layers 23 and 24 may be the same as or different from the shrinkage-inhibiting inorganic material powder contained in the interlayer constraining layer 14 described above.

  The outer constraining layers 23 and 24 are usually formed by previously forming green sheets to be the outer constraining layers 23 and 24 and laminating them on the main surface of the raw laminate 21. In this case, the conductor film 5 located on the outer surface of the raw laminate 21 is formed on at least one of the outer constraining layers 23 and 24, and this is transferred onto the outer surface of the raw laminate 21. You may make it form by doing.

  The outer constraining layers 23 and 24 may be formed by applying an inorganic material paste containing an inorganic material powder for shrinkage suppression onto the main surface of the raw laminate 21. Further, this may be omitted for one of the outer constraining layers 23 and 24. Moreover, in FIG. 4, although the through-hole is formed in the outer constraining layer 23, such a through-hole may not be formed.

  When the steps as described above are performed later so as to obtain a laminated body in which a plurality of multilayer ceramic substrates 1 can be obtained, a raw laminated body 12 is obtained. A break line (not shown) for facilitating division performed later at the stage or when the outer constraining layers 23 and 24 are formed corresponds to a part of the raw laminate 21 in the thickness direction. Formed with depth.

  Next, the raw laminate 21 is fired. This firing step is performed at a temperature at which the ceramic material powder for substrate is sintered but the inorganic material powder for suppressing shrinkage is not substantially sintered. In this firing step, the raw laminate 21 may be pressed in the stacking direction in order to prevent the raw laminate 21 or the multilayer ceramic substrate 1 from undesirably warping.

  In the above-described firing step, the outer constraining layers 23 and 24 are not substantially sintered, and therefore shrinkage due to sintering does not occur. Therefore, it acts on the raw laminate 21 so as to suppress the shrinkage. As a result, the dimensional accuracy in the multilayer ceramic substrate 1 after sintering can be increased. When the firing step is finished, the outer constraining layers 23 and 24 are usually removed from the multilayer ceramic substrate 1 after sintering. This removal can be easily done because the outer constraining layers 23 and 24 are not sintered.

  It should also be noted that the ceramic green layer 22 for substrate contracts more significantly than the interlayer constraining layer 14 in the above-described firing step. Thereby, as well shown in FIG. 1 and FIG. 2, a long protrusion 13 is formed on the inner surface 12 of the cavity 4 by the interlayer constraining layer 14.

  In this reference example, the interlayer constraining layer 14 is formed so as to be located only in the peripheral region of the cavity 4 as well shown in FIG. Thereby, it is possible to make it difficult to cause the problem of warpage that can be encountered when the interlayer constraining layer 14 is formed over the entire surface of the ceramic green layer 22 for a substrate.

  In addition, as a result of the firing process, a part of the material such as the glass component contained in the substrate ceramic green layer 22 penetrates into the interlayer constraining layer 14, thereby fixing the interlayer constraining layer 14. Therefore, the interlayer constraining layer 14 is not removed from the multilayer ceramic substrate 1 as a product.

  Next, plating is performed on the conductor film 5 exposed on the outer surface of the multilayer ceramic substrate 1 after sintering.

  Next, the bonding material 9 is applied on the inner bottom surface 8 of the cavity 4, and the electronic component 7 is bonded to the inner bottom surface 8 of the cavity 4 through the bonding material 9 in a state where the electronic component 7 is disposed on the bonding material 9. The process of carrying out is performed.

  Next, a wire bonding step is performed, and the electronic component 7 and the specific conductor film 5 are electrically connected by the wire 10.

  Thereafter, although not shown, the cavity 4 is sealed with a resin, a surface mount component is mounted on the outer surface of the multilayer ceramic substrate 1, and a metal case is attached so as to cover the surface mount component, if necessary. .

  5 and 6 are for explaining the second reference example. FIG. 5 is a diagram corresponding to FIG. 1 described above, and FIG. 6 is a diagram corresponding to FIG. 2 described above.

  In the first reference example, the interlayer constraining layer 14 is formed in a plurality of layers and the plurality of protrusions 13 are formed. However, the number of the protrusions 13 can be arbitrarily changed. In the multilayer ceramic substrate 1a according to the second reference example, as shown in FIGS. 5 and 6, the interlayer constraining layer 14 is formed along one interface between the substrate ceramic green layers 22, and only one protrusion 13 is formed. It is only formed.

  Also according to the second reference example, if the protruding length L of the protruding portion 13 is made sufficiently large, the creeping of the bonding material 9 can be sufficiently suppressed. In this case, it is preferable that the protruding length L of the protruding portion 13 is 0.01 mm or more.

  In the reference example shown in FIGS. 5 and 6, the protrusion 13 is formed at a height corresponding to the interface between the two ceramic layers 2 closest to the inner bottom surface 8 of the cavity 4. It may be formed at different height positions.

  The second reference example has a characteristic configuration in which the bonding material 9 is prevented from scooping up along the inner surface 12 of the cavity 4 beyond at least the protrusion 13 closest to the opening 3. This characteristic configuration can also be applied to the present invention.

  7 and 8 show a multilayer ceramic substrate 1b according to the first embodiment of the present invention. 7 is a diagram corresponding to FIG. 1, and FIG. 8 is a diagram corresponding to FIG. 7 and 8, elements corresponding to those shown in FIGS. 1 and 3 are denoted by the same reference numerals, and redundant description is omitted.

  The cavity 4 usually provides a rectangular parallelepiped space defined by the four inner surfaces 12. In the first embodiment, as shown in FIGS. 7 and 8, the protruding portion 13 is formed only on one of the two inner side surfaces 12a and 12b facing each other, that is, on the inner side surface 12a. Therefore, the interlayer constraining layer 14 is formed so as to be located only in a part of the peripheral region of the cavity 4, that is, only in a portion along the inner side surface 12a.

  On the other hand, the electronic component 7 has a design in which wire bonding is not performed on at least one of the four sides on the upper surface. More specifically, in FIG. 7, wire bonding is performed on the right side of the electronic component 7, but wire bonding is not performed on the left side.

  Therefore, no protrusion is formed on the inner side surface 12b of the cavity 4 adjacent to the left side of the electronic component 7 as described above, so that even if the joining material 9 creeps up, there is not much problem. Never become.

  On the other hand, since the protruding portion 13 is formed on the inner side surface 12a of the cavity 4 close to the right side of the electronic component 7, the creeping of the bonding material 9 can be effectively suppressed. It is possible to make it difficult to cause a situation that obstructs proper wire bonding.

  FIG. 9 is a view corresponding to FIG. 1 or 7 showing a multilayer ceramic substrate 1c according to the second embodiment of the present invention. In FIG. 9, elements corresponding to those shown in FIG. 1 or FIG.

  In the second embodiment, the electronic component 7a accommodated in the cavity 4 is flip-chip mounted. Therefore, the electronic component 7 a includes a bump electrode 17, and the bump electrode 17 is electrically connected to a conductive land (not shown) formed on the inner bottom surface 8 of the cavity 4.

  On the other hand, in the cavity 4, the protruding portion 13 is formed only on the inner side surface 12 a of the two inner side surfaces 12 a and 12 b facing each other, which are illustrated in FIG. 9. Although not shown in FIG. 9, it is preferable that protrusions are also formed on the other two inner surfaces facing each other of the cavity 4.

  In the second embodiment, after the mounting of the electronic component 7a by the bump electrode 12, the bonding material 9 as an underfill resin is filled between the electronic component 7a and the inner bottom surface 8 of the cavity 4. . In order to introduce the bonding material 9, a nozzle 18 as indicated by an imaginary line in FIG. 9 is used. Therefore, even after the electronic component 7a is mounted, a space for allowing insertion of the nozzle 18 must be left in the cavity 4.

  In order to provide the above-mentioned space, the electronic component 7a is arranged in a state closer to the inner side surface 12a on which the protruding portion 13 is formed. As a result, the joining material 9 tends to creep up on the inner side surface 12a side, but since the protruding portion 13 is formed on the inner side surface 12a, such a scooping up can be performed without increasing the size of the cavity 4. It can be effectively suppressed.

  FIG. 10 is a view corresponding to FIG. 1 and showing a multilayer ceramic substrate 1d as a third reference example outside the scope of the present invention. 10, elements corresponding to those shown in FIG. 1 are denoted by the same reference numerals, and redundant description is omitted.

  In the third reference example, the interlayer constraining layer 14 is formed to extend over the entire surface of the ceramic layer 2. In order to form such an interlayer constrained layer 14, an inorganic material paste containing an inorganic material powder for shrinkage suppression is applied over the entire surface of the ceramic green sheet for a substrate to be the ceramic layer 2, or for shrinkage suppression. A green sheet containing an inorganic material powder may be formed in advance and laminated on a ceramic green sheet for a substrate.

  As described above, when the interlayer constrained layer 14 is formed so as to extend over the entire surface of the ceramic layer 2, warpage in the firing process is likely to occur, so the interlayer constrained layer 14 is balanced in the stacking direction in the raw laminate. It is preferable to arrange well.

  While the present invention has been described above with reference to the illustrated reference examples and embodiments, various other modifications are possible within the scope of the present invention.

  For example, in order to produce the raw laminate 21, in the reference example and the embodiment described above, a plurality of substrate ceramic green sheets to be the substrate ceramic green layer 22 are prepared, and the substrate ceramic green sheets are stacked. However, a structure in which a plurality of substrate ceramic green layers 22 are laminated may be obtained by repeating the step of applying the slurry containing the substrate ceramic material powder.

  Further, in the illustrated reference example and embodiment, the cavity 4 has the step portion 11, but the present invention can also be applied to a multilayer ceramic substrate having a cavity having no step portion.

1, 1a, 1b, 1c, 1d Multilayer ceramic substrate 2 Ceramic layer 3 Opening 4 Cavity 7 Electronic component 8 Inner bottom surface 9 Bonding material 10 Wire 12, 12a, 12b Inner side surface 13 Protruding portion 14 Interlayer constraining layer 17 Bump electrode 21 Laminate 22 Ceramic green layer for substrate 23, 24 Outer constraining layer L Overhang length

Claims (6)

A multilayer ceramic substrate comprising a plurality of laminated ceramic layers and having a cavity that forms an opening on one end side in the lamination direction of the ceramic layers,
An electronic component housed in the cavity, and a bonding material for bonding the inner bottom surface of the cavity and the electronic component;
The cavity provides a rectangular parallelepiped space defined by four inner surfaces, and a longitudinal protrusion extending in a direction parallel to the inner bottom surface of the cavity is formed on the inner surface of the cavity, and the protrusion The portion is not formed on at least one of the four inner surfaces,
Multilayer ceramic substrate.   2. The multilayer ceramic substrate according to claim 1, wherein the plurality of projecting portions are formed so as to be distributed at a plurality of locations having different height positions on the inner side surface of the cavity.   3. The multilayer ceramic substrate according to claim 2, wherein the protruding portion has an overhang length measured in a direction parallel to the inner bottom surface of the cavity of 0.005 to 0.2 mm.   4. The multilayer ceramic substrate according to claim 2, wherein the bonding material is prevented from scooping up along the inner surface of the cavity beyond the protrusion closest to the opening. 5.   2. The multilayer ceramic substrate according to claim 1, wherein the protrusion has an overhang length measured in a direction parallel to the inner bottom surface of the cavity of 0.01 to 0.2 mm.   6. The multilayer ceramic substrate according to claim 1, wherein the bonding material is suppressed from creeping along the inner side surface of the cavity by the protruding portion.

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